A prior art unfolded umbrella is capable of being opened automatically by providing a plurality of springs in a shaft and between a frame and a runner of the umbrella. When the umbrella is closed, the runner is stopped at a lower position of the shaft by a hook in a button mounted on a handle, which is connected with the shaft. When pressing the button, the runner is unlocked and will be moved upward to open the umbrella by use of force of the springs. The above known structure includes many springs that increases the total weight of the umbrella and the assembling procedure is complex and troublesome. Moreover, this known umbrella could be rusted and broken easily and costs high.